Everything you need to know about your sink drainage system

A sink only works when everything goes right behind the scenes. From your kitchen to bathroom sink, having the right drainage setup directs water where it's meant to go, without any surprise leaks or blockages.

This article will go over all the parts of a sink drainage system so that you can choose the best fit for your space and lifestyle.

Where does sink water go?

All sink water, whether it’s from a bathroom, laundry or kitchen sink, ends up in the same wastewater system. However, the plumbing setups used in kitchens, bathrooms and laundries differ slightly to suit how they’re used.

Bathroom sink plumbing is connected to smaller pipes since it mainly collects water, soap and toothpaste.

Kitchen sinks deal with food waste and oils, so they include extra parts to help with the heavy lifting. This is similar to laundry sinks, which handle greater amounts of water and lint.

Under sink plumbing parts

You may not see every part, but each one plays an important role in a smooth running sink. This guide will walk you through the parts of a sink drainage system, from where the water flows in, to where it drains away.

Water supply tube

Sink drainage starts with the water supply. The water supply tube is a flexible pipe that connects the main water supply to your spout. It can be made of materials like PVC, braided nylon or stainless steel.

Basin wastes

A basin waste is the part at the bottom of your sink where water and other waste start moving down to the plumbing. There are different types to suit the room the sink is in and what it’s used for. Choosing the right waste is important in making sure your sink drains properly, without any blockages or overflows.

Most bathroom sinks use a pop-up waste or a plug-and-waste setup, which make it easy to hold or drain water.

• Pop-up wastes: Pop-up wastes use a built-in push mechanism to open or close the drain without needing a separate plug.
• Plug & waste: For a more traditional route, plug & waste systems use a separate plug that you can block the drain with to hold water.

There are also different versions for different kinds of sinks:

• Basket wastes: Sink baskets are usually used in kitchen sinks to catch food scraps, grease and other debris before it travels down the drain. It involves a removable basket that can be lifted out and a lid to block drainage when you want to fill the sink.
• Farmhouse sink wastes: Farmhouse sink wastes are great for large farmhouse basins, with a stainless steel body and durable coating to hide marks.

Tailpieces

A tailpiece is the straight piece of pipe connecting the sink’s drain fitting to the sink trap. It helps guide wastewater from the basin into the rest of the drainage system.

Sink traps

Sink traps stop unwanted odours from escaping the drain. It’s a bit of pipe that catches some of the water as it passes through, creating a seal to stop sewer gases from going back up the pipe.

P-traps and bottle traps are two common options that suit different spaces and plumbing setups. Here’s a rundown of each:

• P-traps: P-traps are used in kitchens, bathrooms and laundries. They have a P-like shape and catch water in the curved part of the pipe. They are also handy for catching small items like pieces of jewellery before they end up further in the drainage system.
• Bottle traps: Bottle traps have a more streamlined, sleek look with a cylindrical body shape. Water drains from the sink, through the vertical part of the trap and into the horizontal section. A small amount of water always stays in the bottom of the trap to stop odours, and the water is pushed through every time you use the sink.

Bottle traps are a popular choice for wall-hung or open bathroom vanities with exposed plumbing, so choose a finish that matches your tapware.

Shut off valve

A shut off valve under the sink is a small valve that lets you switch off its water supply without turning off the entire home’s plumbing. You’d usually find it where the water supply and tapware meet below your sink.

Waste pipe

The waste pipe, often referred to as a drain pipe, is attached to the sink trap and carries the wastewater to the sewer system.

Yabby sink drainage parts

Looking for sink drainage parts? Explore our range of basin wastes and sink traps to get your sink set up properly.

From our basin mixers to door hardware, our products come in six signature finishes so that your fittings match across the board.

Shop from Brushed Brass, Antique Brass, Warm Brushed Nickel, Matte Black, Gunmetal or Chrome colourways, all made from durable materials and designed to fit standard plumbing connections.